cgroup: move cgroup->sibling and ->children into cgroup_subsys_state

We're moving towards using cgroup_subsys_states as the fundamental
structural blocks.  Let's move cgroup->sibling and ->children into
cgroup_subsys_state.  This is pure move without functional change and
only cgroup->self's fields are actually used.  Other csses will make
use of the fields later.

While at it, update init_and_link_css() so that it zeroes the whole
css before initializing it and remove explicit zeroing of ->flags.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index fd538f4c2bb648b70aeae77552403260b9ce04a0..cf8ba26b7c6ec23e7eb7337192ff3e54b5ec81a0 100644 (file)
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -68,6 +68,10 @@ struct cgroup_subsys_state {
        /* PI: the parent css */
        struct cgroup_subsys_state *parent;
 
+       /* siblings list anchored at the parent's ->children */
+       struct list_head sibling;
+       struct list_head children;
+
        /*
         * PI: Subsys-unique ID.  0 is unused and root is always 1.  The
         * matching css can be looked up using css_from_id().
@@ -171,13 +175,6 @@ struct cgroup {
         */
        int populated_cnt;
 
-       /*
-        * We link our 'sibling' struct into our parent's 'children'.
-        * Our children link their 'sibling' into our 'children'.
-        */
-       struct list_head sibling;       /* my parent's children */
-       struct list_head children;      /* my children */
-
        struct kernfs_node *kn;         /* cgroup kernfs entry */
        struct kernfs_node *populated_kn; /* kn for "cgroup.subtree_populated" */
 

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 8c67a739aea46ec70d3bfd0ed2e4e44b5197f159..5385839e727b9412eb34521cbcd4ecbeb5605cfa 100644 (file)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -378,7 +378,7 @@ static int notify_on_release(const struct cgroup *cgrp)
 
 /* iterate over child cgrps, lock should be held throughout iteration */
 #define cgroup_for_each_live_child(child, cgrp)                                \
-       list_for_each_entry((child), &(cgrp)->children, sibling)        \
+       list_for_each_entry((child), &(cgrp)->self.children, self.sibling) \
                if (({ lockdep_assert_held(&cgroup_mutex);              \
                       cgroup_is_dead(child); }))                       \
                        ;                                               \
@@ -870,7 +870,7 @@ static void cgroup_destroy_root(struct cgroup_root *root)
        mutex_lock(&cgroup_mutex);
 
        BUG_ON(atomic_read(&root->nr_cgrps));
-       BUG_ON(!list_empty(&cgrp->children));
+       BUG_ON(!list_empty(&cgrp->self.children));
 
        /* Rebind all subsystems back to the default hierarchy */
        rebind_subsystems(&cgrp_dfl_root, root->subsys_mask);
@@ -1432,7 +1432,7 @@ static int cgroup_remount(struct kernfs_root *kf_root, int *flags, char *data)
        }
 
        /* remounting is not allowed for populated hierarchies */
-       if (!list_empty(&root->cgrp.children)) {
+       if (!list_empty(&root->cgrp.self.children)) {
                ret = -EBUSY;
                goto out_unlock;
        }
@@ -1512,8 +1512,8 @@ static void init_cgroup_housekeeping(struct cgroup *cgrp)
        struct cgroup_subsys *ss;
        int ssid;
 
-       INIT_LIST_HEAD(&cgrp->sibling);
-       INIT_LIST_HEAD(&cgrp->children);
+       INIT_LIST_HEAD(&cgrp->self.sibling);
+       INIT_LIST_HEAD(&cgrp->self.children);
        INIT_LIST_HEAD(&cgrp->cset_links);
        INIT_LIST_HEAD(&cgrp->release_list);
        INIT_LIST_HEAD(&cgrp->pidlists);
@@ -1612,7 +1612,7 @@ static int cgroup_setup_root(struct cgroup_root *root, unsigned int ss_mask)
                link_css_set(&tmp_links, cset, root_cgrp);
        up_write(&css_set_rwsem);
 
-       BUG_ON(!list_empty(&root_cgrp->children));
+       BUG_ON(!list_empty(&root_cgrp->self.children));
        BUG_ON(atomic_read(&root->nr_cgrps) != 1);
 
        kernfs_activate(root_cgrp->kn);
@@ -3128,11 +3128,11 @@ css_next_child(struct cgroup_subsys_state *pos_css,
         * cgroup is removed or iteration and removal race.
         */
        if (!pos) {
-               next = list_entry_rcu(cgrp->children.next, struct cgroup, sibling);
+               next = list_entry_rcu(cgrp->self.children.next, struct cgroup, self.sibling);
        } else if (likely(!cgroup_is_dead(pos))) {
-               next = list_entry_rcu(pos->sibling.next, struct cgroup, sibling);
+               next = list_entry_rcu(pos->self.sibling.next, struct cgroup, self.sibling);
        } else {
-               list_for_each_entry_rcu(next, &cgrp->children, sibling)
+               list_for_each_entry_rcu(next, &cgrp->self.children, self.sibling)
                        if (next->serial_nr > pos->serial_nr)
                                break;
        }
@@ -3142,12 +3142,12 @@ css_next_child(struct cgroup_subsys_state *pos_css,
         * the next sibling; however, it might have @ss disabled.  If so,
         * fast-forward to the next enabled one.
         */
-       while (&next->sibling != &cgrp->children) {
+       while (&next->self.sibling != &cgrp->self.children) {
                struct cgroup_subsys_state *next_css = cgroup_css(next, parent_css->ss);
 
                if (next_css)
                        return next_css;
-               next = list_entry_rcu(next->sibling.next, struct cgroup, sibling);
+               next = list_entry_rcu(next->self.sibling.next, struct cgroup, self.sibling);
        }
        return NULL;
 }
@@ -3283,7 +3283,7 @@ static bool cgroup_has_live_children(struct cgroup *cgrp)
        struct cgroup *child;
 
        rcu_read_lock();
-       list_for_each_entry_rcu(child, &cgrp->children, sibling) {
+       list_for_each_entry_rcu(child, &cgrp->self.children, self.sibling) {
                if (!cgroup_is_dead(child)) {
                        rcu_read_unlock();
                        return true;
@@ -4144,7 +4144,7 @@ static void css_release_work_fn(struct work_struct *work)
        } else {
                /* cgroup release path */
                mutex_lock(&cgroup_mutex);
-               list_del_rcu(&cgrp->sibling);
+               list_del_rcu(&cgrp->self.sibling);
                mutex_unlock(&cgroup_mutex);
 
                cgroup_idr_remove(&cgrp->root->cgroup_idr, cgrp->id);
@@ -4168,9 +4168,11 @@ static void init_and_link_css(struct cgroup_subsys_state *css,
 {
        cgroup_get(cgrp);
 
+       memset(css, 0, sizeof(*css));
        css->cgroup = cgrp;
        css->ss = ss;
-       css->flags = 0;
+       INIT_LIST_HEAD(&css->sibling);
+       INIT_LIST_HEAD(&css->children);
 
        if (cgroup_parent(cgrp)) {
                css->parent = cgroup_css(cgroup_parent(cgrp), ss);
@@ -4344,7 +4346,7 @@ static int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name,
        cgrp->serial_nr = cgroup_serial_nr_next++;
 
        /* allocation complete, commit to creation */
-       list_add_tail_rcu(&cgrp->sibling, &cgroup_parent(cgrp)->children);
+       list_add_tail_rcu(&cgrp->self.sibling, &cgroup_parent(cgrp)->self.children);
        atomic_inc(&root->nr_cgrps);
        cgroup_get(parent);
 
@@ -4507,9 +4509,9 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
                return -EBUSY;
 
        /*
-        * Make sure there's no live children.  We can't test ->children
-        * emptiness as dead children linger on it while being destroyed;
-        * otherwise, "rmdir parent/child parent" may fail with -EBUSY.
+        * Make sure there's no live children.  We can't test emptiness of
+        * ->self.children as dead children linger on it while being
+        * drained; otherwise, "rmdir parent/child parent" may fail.
         */
        if (cgroup_has_live_children(cgrp))
                return -EBUSY;